SiC is the only compound semiconductor from which SiO2 can be thermally grown, which allows SiC to realize all Si MOS device structures. The thermal oxidation of SiC requires a higher oxidation temperature than Si, and the oxidation temperature is as high as 1300° C. At present, the mainstream SiC oxidation process mainly uses an electric resistance heating furnace. The main principle is based on the reaction of silicon carbide with oxygen molecules, but this method of oxidation with oxygen molecules easily causes defects such as residual carbon clusters and oxygen vacancies at the interface. Especially at such high temperatures, in addition to interface oxidation, it also causes interface damage and reduces oxidation efficiency.
In recent years, researchers have proposed a process for oxidizing SiC using microwave plasma to improve the interface quality of SiC oxidation. Microwave plasma generating devices are widely used in the semiconductor industry. The resonant cavity and coupling device are key components of the microwave plasma generating device. In order for the gas to resonate under electromagnetic fields to produce the required plasma, the resonant cavity and the coupling device need to form a strict match, and these two devices have strict dimensional requirements.
Ordinary microwave plasma excitation mainly relies on higher electric field strength, and it is difficult to rely entirely on manual design to implement the reaction cavity conforming to the requirement of generating a large area uniform electric field. The existing microwave plasma generating device has problems such as low efficiency and poor uniformity. In addition, the use of a single discharge unit is likely to cause the risk of operating temperatures being too high or too low.